The 24-year-old had a combined time of 2:05.55minutes from her two runs, too strong for the home crowd favourite Michaela Kirchgasser who had to settle for second, 0.32seconds back.
Third on the day was Germany's Maria Hoefl-Riesch, the overall leader in the World Cup standings, who was another seven hundredths of a second back.
There was to be no denying Gagnon however, who was 13th after the first run but produced a storming second run to top the table, her second effort only beaten by Sweden's Sara Hector.
Austria's Nicole Hosp was fastest after the first round in her home country but could not replicate that effort and had to settle for fourth in the end.
- Sports & Recreation
- Michaela Kirchgasser